Baptism of blood, that is, martyrdom, substitutes for water baptism. It is granted to those who suffer martyrdom for their Christian faith or for the defense of a Christian virtue, since the Lord said: “But whoever loses his life for my sake will find it.” (Mt 10:39) According to the universal teaching of theologians, martyrdom is the patient (non-resistant) endurance of mortal torments for Christ. If any one of the three elements indicated here is missing, it can no longer be considered martyrdom (e.g., the suffering and death of soldiers in war) (cf. Thom. III q. 124 a. 3; cf. Supl. q. 96 a. 6 ad 11; August. Epist. 89, 2; in Ps 34, 2.13; cf. I 153). However, neither desire nor baptism of blood has the sacramental character of baptism. These are rather expressions of the desire for baptism than of the actual sacramental baptism itself.
Already in the Sermon on the Mount, Christ proclaims: “Blessed are those who are persecuted for righteousness’ sake, for theirs is the kingdom of heaven.” (Mt 5:10; cf. Mk 10:38; Lk 12:50) Then: “Whoever acknowledges me before men, I also will acknowledge before my Father who is in heaven.” (Mt 10:32; cf. Mt 10:39; 16:28; Mk 8:35) “Whoever loses his life for my sake will save it.” (Lk 9:24; cf. Jn 12:25) “Greater love has no one than this, that someone lay down his life for his friends.” (Jn 15:13) The Revelation sees the martyrs in the triumphal procession of the heavenly Jerusalem: “These are they who have come out of the great tribulation; they have washed their robes and made them white in the blood of the Lamb. Therefore they are before the throne of God and serve him day and night.” (Rev 7:14–15)
Tradition gives expression to this conviction both in theory and in practice. In theory: “We also have a second bath, which is also unique, namely the bath of blood, of which the Savior says: I have a baptism to be baptized with, and how great is my distress until it is accomplished.” (Lk 12:50) “This is the baptism which replaces the water baptism not received, and restores the one that was lost.” (Tertullian, De Baptismo 16) Cyprian says of the catechumen martyrs: “They are not deprived of the sacrament of baptism, but are baptized in the most glorious and effective way, in the baptism of blood.” According to Saint Augustine, martyrdom has the same efficacy for the forgiveness of sins as water baptism (Cypr. Epist. 73, 22; August. De Civitate Dei XIII 7; Epist. 265, 4; Symbolum ad catechumenos 3, 4). The Greeks speak in the same way (Irenaeus III 16, 4; Cyril of Jerusalem, Catechesis 3, 10; Chrysostom, Homily on the Martyrdom of Lucian 2 [M 50, 522]). This profession of faith is confirmed by the Church’s practice: unbaptized martyrs were honored equally with the baptized (Martyrdom of Perpetua and Felicity 21; Emmerentiana – foster sister of Saint Agnes); and in the feast of the Holy Innocents, from the beginning, it was precisely martyrdom and the heavenly crown gained through martyrdom that were celebrated: “age still unfit for battle was already fit for victory.” (Cypr. Epist. 56, 6; cf. Iren. III 16, 4)
The Roman Martyrology reports on many saints who received only baptism of blood, for when they converted after seeing the martyrdom of Christians and professed themselves as Christians, they were immediately seized and executed. Even young children can receive baptism of blood if they are killed for Christ or for their Christian faith. Such were the infants of Bethlehem, whom Herod had killed, and whose feast the Church celebrates on December 28.
The believing mind first establishes the fact: According to Saint Thomas Aquinas, the power of baptism comes from its identification with the Passion of Jesus Christ and its connection with His cross (Thom. III q. 66 a. 11). This may happen in the ordinary, sacramental way through water baptism; or in an extraordinary, psychic way through perfect love, in which one gives oneself without reserve; and finally, by a special privilege of God, through suffering willingly undertaken for Christ and borne in His spirit, as the greatest proof of love: “Greater love has no one than this, that someone lay down his life for his friends.” (Jn 15:13)
Then it establishes
its efficacy:
a) Baptism of blood agrees with baptism of desire in that it does not impart
the sacramental character; but it agrees with water baptism in that it remits
all sins and punishments. This is sufficiently indicated by the previously
cited statements of Scripture, and is confirmed by the ancient proverb: “He
is unjust to the martyr who prays for the martyr.” (August. Sermo 159,
1; cf. In Joannem 84; Thom. III q. 66 a. 12 ad 1)
b) It exercises this efficacy almost as a physical effect (Thom. III
q. 87 a. 1 ad 2; cf. II-II q. 124 a. 1 ad 1). If it did not operate with
the force of a quasi-physical effect, it would not justify infants, and it
would be difficult to understand how it remits all sins and punishments (as
water baptism does). When we attribute this efficacy almost as a
physical effect, we mean that the torturers are not the instruments chosen by
God for the communication of grace, as is the sacramental sign. Why was baptism
of blood not included by the Council of Trent in the enumeration of the
means of rebirth, along with water and desire baptism? Clearly because baptism
of blood always presupposes the wickedness of persecutors, which God does not
will; and therefore martyrdom cannot simply and in all respects (simpliciter)
be regarded as an instrument of spiritual rebirth willed by God. Martyrdom
belongs to the category about which Saint Augustine says: “God prefers to
bring good out of evil than to allow no evil at all” (I 484): “For those
who love God, all things work together for good.”